Work, Energy and Momentum Flashcards
What is the spring constant of a spring?
The force per unit extension needed to stretch it
What happens if a spring is stretched beyond its limit of proportionality?
It no longer obeys Hooke’s law
What is Hooke’s law?
Force applied = spring constant x extension
Explain what Hooke’s law means?
That the extension of a spring is directly propionate to the force applied to it
provided the limit of proportionality is not exceeded
What is elastic potential energy?
Energy that is stored in an elastic object when work is being done to the object
What happens when the work being done to an elastic object stops?
The elastic energy stored within the object is released
Some transferred as kinetic energy
May make the aroma vibrate more so it becomes warmer
What improvements can be made to help with fuel economy?
- reducing the speed
- fitting a wind deflector
- both reduce the air resistance on the vehicle and so reduce fuel use
What does an anti- skid surface do?
They increase the friction between a car tyre and the road surface
How can you work out the extension of a spring from :
1 length after stretching
2 original length
Spring extension = length after stretching - original length
When is work done on an object?
When a force makes it move
Work done = ?
Energy transferred
How can you work out the work done from :
1 the force
2 distance moved in direction of the force
Work done = Force x distance moved in direction of the force
What is gravitational potential energy?
The energy stored in an object because of its position in the Earth’s gravitational field
What does the gravitational potential energy depend on?2
It’s weight and how far up it moves vertically
What is the kinetic energy of an object?
The energy of that an object has due to its motion
What does kinetic energy depend on?2
Mass and speed
What makes an object elastic?
If it regains its shape after being stretched or squashed
What is he unit of momentum?
Kg m/s
What three things happen when two object push apart? 3
- they move apart
- with a different speed if they have unequal masses
- with equal and opposite momentum, so their momentum is zero
What does the force of the impact depend on when two vehicles collide?3
- mass
- change in velocity (speed)
- duration of impact (time)
If the impact time is longer what happens to the impact force?
The longer the time the less impact force
What is the purpose of crumple zones in a car?
They lessen the force of impact by increasing the impact time
What is another way of expressing the effect of an impact on an object?
G-force
What do seat belts do for you?2
They spread the force across the chest
Increase the impact time
